Groundwater Chemistry in the Mekong River Delta

In the Mekong River Delta, groundwater plays an important role in the functioning of agroecosystems and the activities of local people. It directly affects plant growth and largely determines the specific features of agriculture in the region, which necessitates its detailed study. As part of researches in the Mekong Delta, 27 groundwater samples were collected in November 2022 (the end of the wet season) and analyzed for the content of major ions and total dissolved solids. Hydrochemical types of groundwater were identified, their hierarchical clustering and classification were performed using Kohonen self-organizing maps and the c-means method. A Gibbs diagram was constructed to assess the general mechanisms controlling the chemical composition of groundwater. The principal component method was used to determine the indicators influencing the composition of groundwater. The study revealed groundwater of all four main hydrochemical types in the Mekong Delta. Fresh waters are predominantly of the hydrocarbonate-calcium type, while saline waters are of the chloride-sodium type. Gibbs diagrams and the results of principal component analysis indicate that the intrusion of saline seawater is one of the most important phenomena determining the hydrochemistry of groundwater in the southwest of the Socialist Republic of Vietnam. A boundary between fresh and saline groundwater is fixed in Ben Tre Province. All groundwater samples can be classified into three groups: predominantly fresh water, saline water of Tien Giang Province, and saline water of Ben Tre Province. The data obtained can be used to solve important practical problems in the field of rational nature management in the region.